Timing system



IN'VENTOR ROBERT L.AI CORN,JR.

BY HIS ATTDRNEYS R. L. ALCORN, JR

TIMING SYSTEM Filed Sept. 29, 1949 n mmoT Feb. 19, 1952 Patented Feb. 19, 1952 TIMING SYSTEM Robert L. Alcorn, Jr., Chambersburg, Pa., as-

signor to Chambersburg Engineering Company, Chambersburg, Pa., a corporation of Pennsylvania Application September 29, 1949, Serial No. 118,536

13 Claims. 1

This invention relates to timing devices and more particularly to a novel system for effecting precisely-timed energization of an inductive load.

In certain instances it is desired to effect control of an apparatus by the use of means including an inductive element which may have considerable inertia in the electrical sense. For example, the controlling means may be a solenoid valve whose winding is inherently an inductive element. In some instances it is desired to effect energiz-ation of such an inductive load element for a very short precisely-timed interval which may be a small fraction of a second. Where the inductive load element is energized from a source of unidirectional current, the inertia of said element is very pronounced and causes destructive arcing at relay contacts.

The principal object of the present invention is to provide a novel timing control system which is adapted to effect precisely-timed energization of an inductive load element, and to prevent current arcing in the circuit of said element due to the inductance.

Another object of the invention is to provide a novel timing system of this character in which the timing function is achieved by the charging of a timing capacitor.

A further object of the invention is to provide such a system wherein at least one electron device is utilized and is under control of the timing capacitor.

The invention may be fully understood from the following detail description with reference to the accompanying drawing, wherein Fig. 1 is a diagrammatic illustration of one form of the timing system provided by the present invention; and

Fig. 2 is a diagrammatic illustration Referring first to Fig. 1, there is shown at I0 1 an inductive element which is to be energized from a source of voltage during a precisely timed interval. This element might be the winding of a solenoid valve or it might be any other inductive element.

An A. C. supply line H, operable switch [2 therein, furnishes A. C. current to a powersupply unit 13 which furnishes the voltages for the timing system presently to be described. The power supply unit I3 includes a transformer 14 which serves to supply the filaments of the electron tubes employed, and the unit 13 further comprises a transformer and rectifier arrangement by means of which certain D. C. or unidirectional voltages are obtained. In

having a manually L the particular power supply unit shown, there are a pair of transformers i5 and I6, rectifiers l1, l8 and I9, capacitors 20, 2|, 22 and 23, resistors 24, 25 and 26, and regulator tubes 21 and 28, all connected as shown. This arrangement provides positive voltages, e. g. +150 volts, at the output conductors 29 and 30 with respect to the grounded conductor 3|, and it also provides a negative voltage, e. g. -105 volts, at the output conductor 32 with respect to ground. While the present invention is not concerned with the detained arrangement of the power supply, it might be well to note that in general the conductor 29 supplies direct current of considerable magnitude, but not especially well filtered or regulated, for operating the load Ill, whereas conductor 30 supplies a relatively weak well-filtered and regulated current to the control electron tube as hereinafter described.

In addition to the D. C. voltages, an A. C. control voltage is derived from the supply unit i3 by means of conductors 33 and 34 connected as shown. By means of these conductors, operating voltage is supplied. to a controlling relay 35 and to an overload relay 36. The relay 35 has an operating winding 31 and three sets of contacts 38, 39 and 40. The relay 36 has an operating winding 4| for opening the contacts 42, and a reset winding 43 for closing the contacts. The latter winding is connected across conductors 33 and 34 through a reset switch 44. The operating winding 31 of relay 35 is connected across conductors 33 and 34 through a starting switch 45 and the contacts 42 of relay 35. Contacts of relay 35 are connected in a holding circuit which is in shunt relation with the starting switch 45.

The operating winding 4! of relay 36 is included in a circuit which extends from conductor 29 through the contacts 38 of relay 35, and via conductor 4'! and resistor 48 to one end of the inductive element It, the other end of which is connected to the grounded conductor 49. Conductor 30 is connected through contacts 39 of relay 35 to conductor 41A. Resistors 5G, 5! and 52 are serially connected between conductor 41A and conductor 52. An electron tube 53, which may be a triode as shown, has its cathode grounded, its grid connected through a resistor 54 to a movable tap on resistor 51, and its anode connected to conductor 41A through the winding 55 of a relay 56. A timing capacitor 51 is connected between the grid and cathode of tube 53. The relay 56 serves to control, through its contacts 58, a short circuit about the inductive load I0.

Considering the operation of the system, when the switch I2 is closed, the power supply unit functions to supply the above-mentioned voltages, and the capacitor 5'! is charged to 105 volts by current flow through resistors 5!, 52 and 54, but the system does not operate until the reset switch 44 and the starting switch 45 have been momentarily depressed. The reset switch 44 is first closed momentarily to close the contacts of relay 36; then the starting switch 45 is closed momentarily, thus energizing the relay through the closed contacts of relay 36. The relay 35 locks itself in through its holding contacts 40.

The energization of relay 35 closes the energizing circuit of the inductive load ID and also applies plate voltage to the tube 53. However the grid of tube 53 is biased beyond cut-off by the negative voltage across capacitor 51, and therefore the tube remains non-conductive.

With the closure of relay 35, however, capacitor 51 charges toward a voltage determined by the bleeder resistors 56, 5 i, 52 through resistor 54. When this voltage reaches the cut-oilvoltage of the grid of tube 53, the tube conducts and thus energizes relay 53, which closes the short circuit about the inductive load it]. As a result of this, the current flow through resistor 48 suddenly increases, and the surge of current from the power supply flows through the trip coil 4! of relay 36 which opens contacts 42 and deenergizes relay "35. The opening of the relay contacts 38 and 39 interrupts the main circuit and also removes the plate voltage from tube 53. The system will not operate again until the relay 36 is again reset and starting switch is closed.

It will be seen from the foregoing description that the energization of the inductive load It is precisely timed by the charging of capacitor 51 and is controlled through the operation of tube 53. Moreover, the inductive load is short circuited before the circuit is opened, so that there is no arcing at the contacts.

Referring now to Fig. 2, there is shown therein a preferred embodiment of the invention wherein the control action is effected by means of a dual electron tube, or two separate tubes, as hereinafter described. The inductive load is again shown at 10, and a short-circuiting connection therefor is controlled by the relay 56 as in the first embodiment. The power supply I3 is shown in block form with the voltage supply conductors 29, 30, 32, 33 and 34 extending therefrom.

In this instance, the A. C. control voltage supplied by way of conductors 33 and 34 is utilized .to control relays 59 and 60. The winding 6| of relay 66 is connected across conductors 33 and 34 through a normally open starting switch 62. Contacts 63 of the same relay are included in a holding circuit 64 which is connected in shunt with the starting switch 52 and which may include a stepping switch 65. The winding 66 of relay 59 is connected across conductors 33 and 34 through normally open contacts 6'! of relay 60.

Voltage supply conductor 29 is connected to the ungrounded end of the inductive element [0 through normally open contacts 68 of relay 59 and also through a resistor 59. Voltage supply conductor 36 is connected to the right-hand anode of a doubletriode tube 76 through normally open contacts "H of relay 59, and also through conductor '42 and the winding of relay 56. Conductor 35 is also connected to the lefthand anode of tube 3'3 through a resistor 73.

As described in detail later, the timed ener- -ization of the inductive load 10 is effected through charging of a timing capacitor 14 which is connected between the right-hand grid of tube "it and ground. This capacitor is charged through a resistor 15 from a potentiometer arrangement comprising resistors I6 and 1'! serially connected between conductor 72 and a con ductor 18, the latter beingconnected to conductor 32. The cathodes of tube :9 are connected through a resistor 19 to the conductor 18. The left-hand grid of tube 10 is connected to ground through a resistor 89. The right-hand anode of the tube is connected to the left-hand grid through a capacitor 8i. The left-hand anode is connected to the right-hand grid through a capacitor 82. Voltage supply conductor 32 is connected through normally closed contacts 83 of relay 58 and through a resistor 85 to the ungrounded plate of capacitor 4.

Considering the operation of the system, when the switch I2 is closed, the power supply unit provides the desired voltages but the system will not operate until the starting switch 62 is actuated. With the system in its inoperative state, i. e. prior to actuation of the starting switch, the left-hand triode section of tube 13 is conductive by virtue of the positive voltage applied to the left-hand anode from conductor 36 through resistor 13. Consequently, the voltage drop across resistor 19 maintains the cathodes of the tube at a predetermined negative potential, e. g. -10 volts. At this time, the right-hand triode section of the tube is non-conductive.

Momentary closure of the starting switch 62 energizes relay 5!] which locks itself in through holding circuit 64. The closure of contacts 61 energizes relay 59 which opens its contacts 83 and closes its contacts 68 and I l. The closure of contacts 68 energizes the inductive load In, and at the same time the closure of contacts 1| applies anode voltage to the right-hand triode section of tube 16. The opening of contacts 83 permit the timing capacitor 14 to charge toward a voltage determined by the position of the tap on resistor 76, the rate of charging being determined by the value of resistor 1'5. As a voltage builds up across capacitor 74, the grid of the right-hand triode section of tube 70 is driven to a potential such that the right-hand triode section starts to conduct, and the current flow substantially lowers the voltage at the right-hand anode. This drop in voltage is comunicated by capacitor 8! to the grid of the left-hand section, which causes that section to decrease its anode current flow, thereby increasing its anode voltage. This increase of anode voltage is communicated to the grid of the right-hand triode section by capacitor 82, causing a further increase in anode current and drop of anode voltage of the right-hand section, which is communicated as a voltage drop to the grid of the left-hand section. This action continues and causes rapid cumulative build-up of the current through the winding of relay 56. This current build-up is very abrupt once the capacitor '14 has charged to the critical grid voltage of the righthand triode section. An important advantage of this control action is that it eliminates error due to slight variations in the operating point of relay 53 which would appear as timing errors if a relatively gradual current build-up were employed.

When the relay 56 operates, it closes the shortcircuit connection about the inductive load element l0, thereby effectively deenergizing that element. Following the short-circuiting of element switch 65.

ll, relay- 80 isdeenergized by opening the holding This in turn, deenergizes' relay 5!, and the system is thusrestored to its inoperative state, Theholding switch 65 may be actuated in any. suitable manner. For example, where the controlled device is a solenoid valveand the inductive element In is the-solenoid winding, the holding switch 65' may be automatically" actuated by the movement of the solenoid valve: through a suitable operating arrangement.

It. should be: noted that the, purpose of" the connection controlled by contacts 83 of relay 59 is to cheat positive return of, the charge of capacitor 14 to the normal starting voltage through a circuit with a very small time constant, so that the length of the time interval between operations will have no effect on the duration of the timed interval.

From the foregoing description, it will be seen that both. of the illustrated embodiments eficct precisely timed energization of an inductive load by means of a timing capacitor, and the voltage across the capacitor serves to control a normallyinoperative short-circuitingmeans associated with the inductive load. Further, in each instance; the control actionis effected through the medium of an electron tube. However, in the system of Fig. 2, the control is efiected byv dual tube. action as above described. It will be apparent that in the latter system, twoseparate tubes could be used in place of the double triode I tube which is used only for convenience and simplicity.

By way of specific example, in a certain-physical embodiment of Fig. 2, the tube 10 is a type 6SN7, and the resistors and capacitors have-the following values:

Resistor 69l00 ohms--50 w. Resistor IS-75,000 ohms-1 w. Resistor 15-1,-megohm1 w. Resistor 16-250,000' ohms Resistor '|'l---150,000 ohms1 w. Resistor 1950,000 ohms-1 w. Resistor 80-1 meg0hm w. Resistor 84--1,000 ohms-2 w. Capacitor 14-.3 microfarad Capacitor 81-500 micro-microfarads Capacitor 82-500 micro-microfarads Of course it will be understood that the circuit elements may be varied at will according to the particular application of the system.

The present invention is applicable in any instance where it is desired to efi'ectprecisely timed energization of an inductive load. By way of example, the invention is applicable to a drop 1. In asystem for efiecting precisely timed energization of an inductive load from a source of voltage, a normally-open circuit extending between said source and said inductive load, anormally-open short-circuiting connection, across said inductive load, a pair. of triodesone' of which is normally conductive and the other of which is normally non-conductive, a normally deenergized relay for controlling said short-circuiting connection, the winding of said relay being'connected in the plate circuitor the normally nonconductive triode, av timing capacitor connected to the gridof the latter triode to, control the same; means for closing. the first-recited circuit and for simultaneously initiating the charging of said capacitor, whereby the normally nonconductive triode starts to conduct when the voltage across said capacitor reaches a certain value, and connections between the elements of said triodes to efiect rapid build up of current through said relay winding, whereby said relay is energized to close said short-circuiting connection at the end of a time interval determined by the charging of said capacitor.

2. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open circuit extending between said source and said inductive load, a nornially-open short-circuiting connection across said inductive load, a pair of triodes one ofwhich is normally conductive and the other of which is normally non-conductive, a normally deenergized relay for controlling said short-circuiting connection, the winding of said relay being'connected in the plate circuit of the normallynonconductive triode,- a timing capacitor connected to the grid-of the lattertriode to control the same, means for closing the first-recited circuit and for simultaneously initiating the charging of said capacitor, whereby the normally non-conductive triodestarts to conduct when the voltage across said capacitor'reaches a certain value, and a connection between the anode of each triode and the grid of the other triode to effect rapid build up of current through said relay winding, whereby said-relay is energized'to close said short-circuiting connection at the end 01" av time interval determined by the charging of said capacitor;

3. In a system for effecting precisely timed energization of an inductiv load from a soruce of voltage, a normally-open circuit extending between. said source andv said inductive load, normally-inoperative means for short-circuiting said inductive load, a pair of triodesone of which is normally conductive and theother of which is normally non-conductive, means controllable by the normally non-conductive triode to render saidashort-circuiting-means operative upon conduction of that triode, a timing capacitor connectedto the grid of the latter triode to control the same, means for closing the first-recited circult and for simultaneously initiating the charging of said capacitor, whereby the normally nonconductive triode starts to conduct when the voltage across said capacitor reaches a certain value", and connections between the elements of said. triodes to efiect rapid build-up of current through the normally non-conductive triode, whereby said short-circuiting means is rendered operative at-tlie end of a time interval determined by the charging of said capacitor.

4. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open circuit extending between said source and said inductive load, normally-inoperative means for short-circuiting said inductive load, a pair of triodes one of which is normally conductive and the other of which is normally non-conductive, means controllable by the normally non-conductive triode to render said short-circuiting means operative upon conduction of that triode, a timin capacitor connected to the grid of the latter triode to control the same, means for closing th first-recited circuit and for simultaneously initiating change of en- -ergy stored by said. capacitor, whereby the normally non-conductive triode starts to conduct when the voltage across said capacitor reaches a certain value, and connections between the elements of said triodes to effect rapid bui1dup of current through the normally non-conductive triode, whereby said short-circuiting means is rendered operative at the end of a time interval determined by the change of energy stored by said capacitor.

, 5. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open circuit extending between said source and said inductive load, normally-inoperative means for short-circuiting said inductive load, a pair of triodes one of which is normally conductive and the other of which is normally non-conductive, means controllable by the normally non-conductive triode to render said shcrt-circuiting means operative upon conduction of that triode, a timing capacitor connected to the grid of the latter triode to control the same, means for closing the first-recited circuit and for simultaneously initiating the charging of said capacitor, whereby the normally nonconductive triode starts to conduct when the voltage across said capacitor reaches a certain value, and a connection between the anode of each triode and the grid of the other triode to effect rapid build-up of current through the normally non-conductive triode, whereby said short-circuiting means is rendered operative at the end of a time interval determined by the charging of said capacitor.

6. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open circuit extending between said source and said inductive load, normally-inoperative means for short-circuiting said inductive load, a pair of triodes one of which is normally conductive and the other of which is normally non-conductive, means controllable by the normally non-conductive triode to render said short-circuiting means operative upon conduction of that triode, a timing capacitor con nected to the grid of the latter triode to control the same, means for closing the first-recited circuit and for simultaneously initiating change of energy stored by said capacitor, whereby the normally non-conductive triode starts to conduct when the voltage across said capacitor reaches a certain value, and a connection between the anode of each triode and the grid of the other triode to effect rapid build-up of current through the normally non-conductive triode, whereby said short-circuiting means is rendered operative at the end of a time interval determined by the change of energy stored by said capacitor.

7. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open circuit extending between said source and said inductive load, normany-inoperative means for short-circuiting said inductive load, electron tube means comprising a pair of grid-controlled tube units one of which is normally conductive and the other of which is normally non-conductive, means controllable by the normally non-conductive tube unit to render said short-circuiting means operative upon conduction of that tube unit, a timing capacitor connected to the control grid of the latter tube unit. to control the same, means for closing the first-recited circuit and for simultaneously initiating change of energy stored by said capacitor, whereby the normally non-conductive tube unit starts to conduct when the voltage across said capacitor reaches a certain value, and connections between the elements of said tube units to effect rapid build-up of current through the normally non-conductive tube unit, whereby said short-circuiting means is rendered operative at the end of a time interval determined by the change of energy stored by said capacitor;

8. In a system for eifecting precisely timed energization of an inductive load from a source of voltage, a normally-open circuit extending between said source and said inductive load, normany-inoperative means for short-circuiting said inductive load, electron tube means comprising a pair of tube units having triode elements, one of which tube units is normally conductive and the other of which is normally non-conductive, means controllable by the normally non-conductive tube unit to render said short-circuiting means operative upon conduction of that tube unit, a timing capacitor connected to the control grid of the latter tube unit to control the same, means for closing the first-recited circuit and for simultaneously initiating change of energy stored by said capacitor, whereby the normally non-conductive tube unit starts to conduct when the voltage across said capacitor reaches a certain value, and a connection between the anode of each tube unit and the control grid of the other tube unit to effect rapid build-up of current through the normally non-conductive tube unit, whereby said 'short-circuiting means is rendered operative at the end of a time interval determined by the change of energy stored by said capacitor.

9. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open load circuit extending between said source and said inductive load, a normally-open short-circuiting connection across said inductive load, a normally non-conductive electron tube unit having triode elements, means controllable by said tube unit for closing said short-circuiting connection, a timing capacitor connected to the control grid of said tube unit to control the same, a normally-deenergized control relay having normally-open contacts included in said load circuit and in the plate circuit of said tube unit to close those circuits upon energization of the control relay, means including a manual switch to be closed momentarily for energizing said control relay, means for holding in said control relay after opening of said switch, means controlled by said control relay for initiating change of energy stored by said capacitor, whereby said tube unit starts to conduct when the voltage across said capacitor reaches a certain value, and said short-circuiting connection is closed at the end of a time interval determined by the change of energy stored by said capacitor, and means for deenergizing said control relay after closure of said short-circuiting connection, thereby to condition the system for repeat operation.

10. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open load circuit extending between said source and said inductive load, a normally-open short-circuiting connection across said inductive load, a normally non-con ductive electron tube unit having triode elements, means controllable by said tube unit for closing said short-circuiting connection, a timing capacitor connected to the control grid of said tube unit to control the same, a normally-deenergized control relay having normally-open contacts included in said load circuit and in the plate circuit of said tube unit to close those circuits upon energiaation of the control relay, means including a manual switch to be closed momentarily for energizing said control relay, means for holding in said con trol relay after opening of said switch, means controlled by said control relay for initiating change of energy stored by said capacitor, whereby said tube unit starts to conduct when the volt age across said capacitor reaches a certain value, and said short-circuiting connection is closed at the end of a time interval determined by the change of energy stored by said capacitor, an overload relay having a winding included in said load circuit and having contacts arranged to deenergize said control relay in response to increased current flow in said load circuit upon short-circuiting of said inductive load.

11. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open load circuit extending between said source and said inductive load, a normally-open short-circuiting connection across said inductive load, electron tube means comprising a pair of grid-controlled tube units one of which is normally conductive and the other i energization of the control relay, means including a manual switch to be closed momentarily for energizing said control relay, means for holding in said control relay after opening of said switch, means controlled by said control relay for initiating change of energy stored by said capacitor, where the normally non-conductive tube unit starts to conduct when the voltage across said capacitor reaches a certain value, connections between the elements of said tube units to effect rapid build-up of current through the normally non-conductive tube unit, whereby said short-circuiting connection is closed at the end of a, time interval determined by the change of energy stored by said capacitor, and means for deenergizing said control relay after closure of said short-circuiting connection, thereby to condition the system for repeat operation.

12. In a system for effecting precisely timed energization of an inductive load from a source of voltage, a normally-open load circuit extending between said source and said inductive load, a normally-open short-circuiting connection across said inductive load, electron tube means comprising a pair of grid-controlled tube units one of which is normally conductive and the other of which is normally non-conductive, means controllable by the normally non-conductive tube unit for closing said short-circuiting connection, a timing capacitor connected to the control grid of the latter tube unit to control the same, a normally deenergized control relay having normally-open contacts included in said load circuit and in the plate circuit of the normally non-conductive tube unit to close those circuits upon energization of the control relay, means including a manual switch to be closed momentarily for energizing said control relay, means for holding in said control relay after opening of said switch, means controlled by said control relay for initiating chage of ener y stored by said capacitor, whereby the normally non-conductive tube unit starts to conduct when the voltage across said capacitor reaches a certain value, a connection between the anode of each tube unit and the grid of the other tube unit to effect rapid build-up of current through the normall non-conductive tube unit, whereby said short-circuiting connection is closed at the end of a time interval determined by the change of energy stored by said capacitor, and means for deenergizing said control relay after closure of said short-circuiting connection, thereby to condition the system for repeat operation.

13. In a system for effecting precisely timed energization of an electrical load from a source of voltage, a normally-open load circuit extending between said source and said load, a normally non-conductive electron tube unit having triode elements, a timing capacitor connected to the control grid of said tube unit to control the same, a normally-deenergized control relay hav ing normally-open contacts included in said load circuit and in the plate circuit of said tube unit to close those circuits upon energization of the control relay, means including a manual switch to be closed momentarily for energizing said control relay, means for holding in said control relay after opening of said switch, means controlled by said control relay for initiating change of energy stored by said capacitor, whereby said tube unit starts to conduct when the voltage across said capacitor reaches a certain value, means controlled by said tube to effect deenergization of said load, and means for deenergizing said control relay to condition the system for repeat operation.

ROBERT L. ALCORN, JR.

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